Portable electrophotographic powder-image transfer mechanism



Jan. 27, 1953 Filed May 8, 1951 c. R; MAYo EFAL 2,626,355 PORTABLE ELECTROPHOTOGRAPHIC POWER-IMAGE TRANSFER MECHANISM 2. SHEETS-SHEET l A TTORIVEY Jan. 27, "1953 c. R. MAYO EIAL 2,626,365

' PORTABLE ELECTROPHOTOGRAPHIC POWER-IMAGE TRANSFER MECHANISM Filed May a, 1951 2 SHEETS-SHEET 2 \L) (Q) I INVENTORS' 0L YDE R. MAYO ROBERT ll BENSON Patented Jan. 27, 1953 PORTABLE ELECTROPHOTOGRAPHIC POWDER-IMAGE TRANSFER MECH- ANISM Clyde R. Mayo, Brighton, and Robert W. Benson,

Brockport, N. Y., assignors to The Haloid Company, Rochester, N. Y., a corporation of New York Application May 8, 1951, Serial No. 225,234

9 Claims.

This invention relates to portable mechanism for transferring a powder-image from an insulating layer on to a sheet of transfer material such as paper, with particular reference to transferring a powder-image from an electrophotographic plate to a transfer sheet by electrostatic action as in electrophotographic processes, and it has for its purpose to afford a simple, practical and efficient mechanism that is compact, of light weight, and which can readily be positioned in contact with and moved in any selected path over a sheet of paper to which a powderimage is to be transferred and without the necessity of a fixed relationship between the transfer mechanism and paper.

In the operation of transferring a powderimage from an electrophotographic plate to a sheet of paper, the usual procedure and mechanism has limited the size of the sheet of paper that can be positioned in the transfer apparatus and has also limited the position in which the powder-image can be located on the transfer sheet, and it is a particular purpose of this invention to provide a portable mechanism of such construction that any portion of a transfer sheet can be located in contact with the insulating layer and the powder-image transferred to and located on any desired portion on the transfer sheet.

Another object of the invention is to afford a structure in which a portable transfer mechanism is a complete self-contained unit including electric discharge means which can be moved Over the insulating layer and transfer material.

A further purpose of the invention is to provide a portable powder-image transfer mechanism with means for readily supporting the structure'on and moving it over a sheet of paper and an insulating layer.

Still an additional object of the invention is to provide a portable transfer mechanism with instrumentalities for holding a sheet of paper or transfer material in intimate uniform contact with an insulating layer while the discharge means is moved thereacross and an electrostatic charge applied to the transfer sheet.

To these and other ends, the invention consists in the construction and arrangement of parts that will appear clearly from the following description when read in conjunction with the accompanying drawings, the novel features being pointed out in the claims following the specification.

In the drawings:

Fig.1 is a plan view of an apparatus construct- 2 ed in accordance with a preferred embodiment of the invention, and showing it in position on a plate or bed ready for movement over a sheet of paper arranged on a powder-image and an insulating layer of an electrophotographic plate, the position of the transfer mechanism after it has been moved across the transfer sheet being indicated in dotted lines;

Fig. 2 is a view in side elevation of the parts illustrated in Fig. 1;

Fig. 3 is a sectional view taken on line 3-3 of Fig. 1 looking in the direction indicated, and showing the transfer mechanism moved partially across the transfer sheet and insulating layer;

Fig. 4. is a sectional view on line 4-4 of Fig. 3 looking in the direction indicated;

Fig. 5 is a sectional view on line 5-5 of Fig. 3, looking in the direction indicated;

Fig. 6 is a detail perspective view of the frame secured within the housing, and

Fig. 7 is a diagrammatic view of the electrical circuit arrangement.

The invention may be carried out in a variety of ways and with different types of apparatus, of which the structure herein shown is a practical example, and referring more particularly to the drawings in which like reference numerals refer to the same parts throughout the several views, there is provided a housing of generally inverted U-shaped cross-section, open at the bottom and ends, and including a top wall I and side walls 2 terminating at their lower edges in outwardly turned flanges 3.

Secured interiorly of the housing is a conductive frame upon which the electrical discharge units are mounted, and consisting of a bottom wall 4 coextensive endwise with the housing 2, and upstanding side walls 5 which abut the side walls 2 of the housing and are attached thereto by suitable fastening means 6, while I designate depending end walls formed integral with the bottom wall 4 of the frame andpreferably spaced at their edges from the side walls 2 of the housing. The depending walls '1 of the frame are attached at their lower ends to connecting plates 8 forming part of the carriage and having journalled therein the rolls 9 provided with pintles I I engaging openings in the connecting plates 8, while 12 designate cylindrical sleeves formed of rubber or other suitable material affording soft resilient peripheries for the rolls 9 and which contact and travel over the transfer paper to hold the latter uniformly in close intimate contact with the powder image and insulating layer. Thus the carriage through the rolls 9, connecting plates 8, end walls I, and housing support the electrical charging mechanism which will be described presently.

The lower edges of the side walls 2 of the housing are spaced somewhat above the lowermost portion of the rolls 9 and above the surface of the paper or transfer sheet, so that when a sheet of transfer material is laid over a powderimage on an insulating layer, the charging apparatus may be moved over any portion of the transfer sheet or in any selected ath with reference to the transfer sheet. This enables transference of a powder-image to any part of the surface of the paper on to which the image is to be afiixed. Thus if a sheet contains a drawing to which it is desired to make an addition, such addition can be completed on a separate piece of paper and after making a powder-image thereof electrophotographically, the powderimage can be transferred to the first sheet in exactly the desired location with reference to the first drawing.

Position of the image on the transfer sheet is not limited by insertion of the heet into a predetermined position in a transfer apparatus as in machines such as heretofore used, while at the same time the paper is held intimately in contact with the powder-image and insulating layer by means of the rolls 9, one of which engages the transfer material in advance of the discharge apparatus and holds it closely against the image and insualting layer, as a result of which the powder-image is transferred with a maximum degree of accuracy and faithfulness of reproduction.

The transfer apparatus may be employed in connection with any suitable ground plate such as indicated at l3, having a recess to receive the electrophotographic plate I4 and insulating layer carrying a powder-image, while l5 designates the paper or transfer sheet positioned in contact with the powder-image and insulating layer so as to receive the image when an electrostatic charge is sprayed on to the transfer sheet in the manner that will be presently described.

The charge may be imposed on the transfer sheet by various types of electrostatic charging units and in the construction shown, which constitutes one effective and practical charging arrangement, there is provided a corona discharge electrode consisting of one or more corona wires l6 which may extend parallel to the rolls 9 perpendicular to the path of movement of the mechanism across the sheet, and are secured at their ends to walls of suitable insulating blocks I! which are located underneath the wall t at the ends thereof and attached by suitable fastening devices l8.

The insulating blocks H are cut away to afford shoulders l9 to which the corona electrode wires 16 are fastened, while 2| designate wires of a corona control electrode, preferably located in parallel relation to the wires l6 beneath the latter and attached to bottom surfaces of the insulating blocks IT, as shown in Figs. 3 and 4. The insulating blocks ll are cut away at their lower edges to afford horizontal portions at the bottom and upwardly inclined portions extending from their bottom edges to their side edges, whereby the bottom wires of the corona control electrode are arranged in a horizontal plane and other wires are arranged in upwardly inclined planes at the ends of the horizontal plane, as illustrated in Fig. 3. This arrangement affords an eficient disposition of the wires of the control electrode which acts to 4 limit the potential of the charge on the transfer sheet, while the bottom wall 4 of the interior frame, which is of metal Or other conductive material, functions as a shield above the corona discharge electrode to intensify the effect of the corona electrode.

The corona electrode is connected to a high voltage source while the control electrode is connected to a low potential source. The corona electrode charges the plate until the potential of its charge about equals that of the control electrode, after which the corona spray travels from the corona electrode to the control electrode instead of to the transfer sheet.

The corona wires l6 and 2! are suitably fastened to the insulating blocks I7 and connected through conductors 22 and 23 respectively, see Fig. '7, to a power pack 2 of conventional form located apart from the portable apparatus which forms the subject matter of this invention and connected thereto by flexible cords or cables. 25 and 28 designate conductors leading from the source of power and from power pack 24 to a switch 21 suitably mounted in a switch box 28 secured against a wall 29 of the bracing member =35 which is attached to the side walls 2 of the housing. 32 is a conductor leading from the power source to the power pack 24, as shown in Fig. 7, and 33 designates a conductor leading from switch 21 tothe conductive shield 4 which is connected to power pack 24 and grounded through conductor 34.

The grounded shield 4 is connected to conductors 33 and 34 in any suitable fashion, as well known in the art, and conductors 25, 26 and 34 are carried through a flexible cord 35 connected with the power pack and power source, while conductors 22 and 23 are carried through a flexible cord 36 to the power pack 24.

The power pack 24 is connected to a source of electrical current, such as a 110 volt 6'0 cycle alternating current and affords an external high potential source for the corona discharge wires [6 and for the control electrode wires 2| which are connected to a source of lower potential than the corona discharge wires IE, while the shield 4 is held at a low potential or connected to ground with respect to the discharge wires IS.

A potential of from 3000 to 7000 volts and usually about 6000 to 7000 volts is applied between the corona discharge wires !6 and the nearest conductors or electrodes in order to produce a satisfactory corona discharge, and preferably such voltage is less than 10,000 volts in order to avoid sparking or excessive space charges, and the corona discharge wires can be made either the positive or negative terminal of the potential source depending on the polarity of the charge desired on the insulating layer.

The voltage applied between the control electrode and the transfer sheet is preferably a D. C. voltage of from to 1000 volts, or optionally a pulsating voltage synchronized with a pulsating corona discharge voltage. With D. C'. corona discharge, the potential of the control electrode can be intermediate. to the potential of the corona discharge electrode on one hand and the potential of the transfer sheet which usually is originally at ground potential or it may be the same as the potential of the transfer sheet or, in some cases, ground potential, or the original potential of the transfer sheet may be intermediate to the corona potential and the control elece trode potential. However, when the device is operating in the transfer of an, image from a xerographic plate, the voltage between the control electrode and the conductive backing of such plate is kept below the breakdown voltage of the insulating layer from which the image is being transferred. Thus, with the usual xerographic plates, this voltage does not exceed 1000' volts and generally is maintained substantially below about 500 volts.

. While the above indicates generally the method of energizing the corona discharge electrode, the control electrode, and the shield, the particular charging voltages and electrical circuit arrangements form no part of the present invention, which has to do only a portable apparatus and the necessary electrical units mounted thereon for movement over a transfer sheet in any selected path to effect spraying of a charge on to any part of a transfer sheet and xerographic plate, whereby a powder-image is transferred from the insulating layer of the xerographic plate to the selected portion of the transfer paper.

The operation of the device briefly is as follows: a xerographic plate, bearing a powderimage previously imposed thereon by dusting an electrophotographic image with powder, is positioned in the recess of the ground plate 13 with the powder-image facing upwardly, and with the surface of the xerograpnic plate flush with the surface of the ground plate. The transfer mechanism is then placed on the ground plate to one side of the recess and xerographic plate and a sheet of paper is placed down on the xerographic plate with any selected part of the paper in contact with the powder-image on the xerographic plate, after which the switch 2! is operated to close the electrical circuits. Following this, the operator manually pushes the transfer mechanism across the xerographic plate, during which the rolls 9 hold the paper in close uniform contact with the powder-image and xerographic plate and a proper electrostatic charge is sprayed onto the paper resulting in a transfer of the electroscopic powder-image from the xerographic plate to the paper sheet.

While the invention has been described with reference to the structure herein shown, it is not confined to the details disclosed and this application is intended to cover such changes and departures as may come within the purposes of the invention and the scope of the following claims.

We claim:

1. A portable electrophotographic powderimage transfer mechanism comprising a carriage movable over a sheet of transfer material and including rolls coextensive in length with the width of the carriage and having continuous contact with the transfer material perpendicularly of their path of movement, and electrical discharge means comprising corona discharge wires connected to an external high voltage source and mounted on said carriage above the lowermost portions of the carriage entirely between said rolls whereby the electrical discharge means is movable in a selected path and over any portion of a sheet to which a powder-image is to be transferred whereby the sheet of transfer material is engaged and held throughout its width by said rolls.

2. A portable electrophotographic powderimage transfer mechanism comprising a carriage movable over a sheet of transfer material and including rolls coextensive in length with the width of the carriage and having continuous contact with the transfer material perpendicularly of their path of movement, a housing mounted on said carriage entirely between said rolls with the lowermost part of the housing above the lowermost portions of the carriage and beneath the tops of said rolls, and electrical discharge means comprising corona discharge wires connected to an external high voltage source and mounted in said housing entirely between said rolls whereby the electrical discharge means is movable in a selected path and over any portion of a sheet to which a powder-image is to be transferred whereby the sheet of transfer material is engaged and held throughout its width by said rolls.

3. A portable electrophotographic powderimage transfer mechanism comprising a carriage including a pair of spaced parallel rolls coextensive in length with the width of the carriage and movable over a sheet of transfer material and having continuous contact therewith perpendicularly of their path of movement, and electrical discharge means comprising corona discharge wires connected to an external high voltage source and mounted on said carriage and arranged entirely between said rolls above the lowermost portions of the rolls whereby the electrical discharge means is movable in a selected path and over any portion of a sheet to which a powder-image is to be transferred whereby the sheet of transfer material is engaged and held throughout its width by said rolls.

4. A portable electrophotographic powderimage transfer mechanism comprising a carriage including a pair of spaced parallel rolls coexten sive in length with the width of the carriage and movable over a sheet of transfer material and having continuous contact therewith perpendicularly of their path of movement, a housing mounted on said carriage between said rolls with the lowermost part of the housing located above the lowermost portions of the rolls and beneath the tops of the rolls, and electrical discharge means comprising corona discharge wires connected to an external high voltage source and mounted in said housing entirely between said rolls above the lowermost portions of the rolls whereby the electrical discharge means is movable in a selected path and over any portion of a sheet to which a powder-image is to be transferred whereby the sheet of transfer material is engaged and held throughout its width by said rolls.

5. A portable electrophotographic powderimage transfer mechanism comprising a carriage including a pair of spaced parallel rolls coextensive in length with the width of the carriage and movable over a sheet of transfer material and having continuous contact therewith perpendicularly of their path of movement, a housing mounted on said carriage between said rolls with the lowermost part of the housing located above the lowermost portions of the rolls and beneath the tops of the rolls, and electrical discharge means comprising corona discharge wires located in the housing above the rolls and a series of fixed uniformly spaced corona discharge control wires located in the housing in a plane below the top and above the bottom portions of the rolls.

6. A portable electrophotographic powderimage transfer mechanism comprising a carriage including a pair of spaced parallel rolls coextensive in length with the width of the carriage and movable over a sheet of transfer material, a pair of connecting plates on which said rolls are mounted, a housing mounted on said carriage between said rolls with the lowermost part of the housing located above the lowermost portions of the rolls and beneath the tops of the rolls, said housing including top and side walls and open at its ends and bottom, a conductive frame including a horizontally disposed bottom wall constituting a grounded shield, said frame also including upstanding side walls abutting and attached to the side walls of the housing and depending end walls attached to said connecting plates, insulating blocks located beneath said bottom wall at its ends and attached thereto, corona discharge wires located beneath said grounded shield and extending between and attached to said insulating blocks, and a series of fixed uniformly spaced corona discharge control wires extending between and attached to said insulating blocks beneath the corona discharge wires and above the lowermost portions of the rolls.

7. A portable electrophotographic powderimage transfer mechanism comprising a carriage including a pair of spaced parallel rolls coextensive in length with the width of the carriage and provided with resilient peripheries movable over a sheet of transfer material and having con-= tinuous contact therewith perpendicularly of their path of movement, a pair of connecting plates on which said rolls are mounted, a hous ing mounted on said carriage between said rolls with the lowermost part of the housing located above the lowermost portions of the rolls and beneath the tops of the rolls, said housing including top and side walls and open at its ends and bottom, a conductive frame including a horizontally disposed bottom wall constituting a grounded shield, said frame also including upstanding side walls abutting and attached to the side walls of the housing and depending end walls attached to said connecting plates, insulating blocks located beneath said bottom wall at it's ends and attached thereto, corona discharge wires located beneath said grounded shield and extending between and attached to said insulating blocks, and a series of fixed uniformly spaced corona discharge control wires extending between and attached to said insulating blocks beneath the discharge wires and above the lowermost portions of the rolls.

8. A portable electrophotographic powderirnage transfer mechanism comprising a carriage including a pair of spaced parallel rolls coextensive in length with the width of the carriage and movable over a sheet of transfer material, a pair of connecting plates on which said rolls are mounted, a housing mounted on said carriage between said rolls with the lowermost part of the housing located above the lowermost portions of the rolls and beneath the tops of the rolls, said housing including top and side walls and open at its ends and bottom, said side walls extending downward between said rolls and terminating in spaced relation above the lowering plates and extending downwardly to the lowermost portions of the connecting plates, insulating blocks located beneath said bottom wall at its ends and attached thereto, corona discharge wires located beneath said grounded shield and extending between and attached to the insulating blocks, and a series of fixed uniformly spaced corona discharge control wires extending between and attached to said insulating blocks beneath the corona discharge .wires and in a plane between the top and bottom portions of said rolls.

9. In a portable electrophotographic powderimage transfer mechanism, the combination with a ground plate having a recess in which is positioned an electrophotographic plate carrying a powder-image and a transfer sheet superposed on said powder-image, the top surface of the ground plate surrounding the transfer sheet and located in the same horizontal plane with the top surface of the transfer sheet, of a transfer mechanism comprising a carriage movable over said powder-image and transfer sheet and including a pair of spaced parallel rolls coextensive in length with the width of the carriage and having continuous contact with the transfer sheet perpendicularly to the direction of movement of the carriage, and electrical discharge means comprising corona discharge wires connected to an external high voltage source and mounted on said carriage above the lowermost portions of the carriage whereby the electrical discharge means is movable in a selected path and over any portion of a sheet to which a powder-image is to be transferred whereby the sheet of transfer material is engaged and held throughout its width by said rolls.

CLYDE R. MAYO. ROBERT W. BENSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 443,798 Schaeffer Dec. 30, 1890 940,429 Chapman Nov. 16, 1909 940,430 Chapman Nov. 16, 1909 1,141,295 Wright June 1, 1915 2,270,526 Keyser et al. Jan. 20-, 1942 2,333,213 Slayter Nov. 2, 1943 2,377,391 White June 5, 1945 2,543,051 Oughton et al Feb. 27, 1951 2,564,126 Neece Aug. 14, 1951 FOREIGN PATENTS Number Country Date 699,025 Germany Nov. 21, 1940 

1. A PORTABLE ELECTROPHOTOGRAPHIC POWDERIMAGE TRANSFER MECHANISM COMPRISING A CARRIAGE MOVABLE OVER A SHEET OF TRANSFER MATERIAL AND INCLUDING ROLLS COEXTENSIVE IN LENGTH WITH THE WIDTH OF THE CARRIAGE AND HAVING CONTINUOUS CONTACT WITH THE TRANSFER MATERIAL PERPENDICULARLY OF THEIR PATH OF MOVEMENT, AND ELECTRICAL DISCHARGE MEANS COMPRISING CORONA DISCHARGE WIRES CONNECTED TO AN EXTERNAL HIGH VOLTAGE SOURCE AND MOUNTED ON SAID CARRIAGE ABOVE THE LOWERMOST PORTIONS OF THE CARRIAGE ENTIRELY BETWEEN SAID ROLLS WHEREBY THE ELECTRICAL DISCHARGE MEANS IS MOVABLE IN A SELECTED PATH AND OVER ANY PORTION OF A SHEET TO WHICH A POWDER-IMAGE 